1. Field of the Invention
The present invention is a tank for removing sand and other particulate matter or solids from a water stream. The tank is provided with a conical bottom to aid in the frequent removal of separated solids from the tank.
2. Description of the Related Art
Various tank designs have been developed for removing solids from a water stream, such as atmospheric vertical oilfield tanks designed for treating oilfield fluid streams entering a production or processing facility.
One particularly effective solids removal tank is taught U.S. patent application Ser. No. 14/090,477 which was filed on Nov. 26, 2013 for Desanding, Flow Splitting, Degassing Vessel. That patent application teaches a tank for removing sand and other particulate matter or solids from a water stream. In addition to removing solids from the water stream, that tank is designed to remove associated gases and eliminate their inherent mixing energies from the inlet fluid stream, and to divide the outgoing water flow hydraulically and evenly into two or more effluent streams.
That tank works well in separating the solids from the water, but it does have one flaw. The flaw is that the solids that are removed from the water stream tend to accumulate in the flat bottom of the tank and are not easily removed from the flat tank bottom. Because the solids cannot be easily removed, eventually the solids will fill the tank and the tank will have to be removed from service so that the solids can be removed manually.
The present invention addresses this problem by providing a traditional straight sided tank having a vertical exterior wall such as the one taught in U.S. patent application Ser. No. 14/090,477 that is modified to provide the tank with an interior conical bottom.
Solids that accumulate in the conical bottom of this tank can be more effectively removed on a daily basis, extending the time in which the tank may be operated without taking it out of service for maintenance. A solids outlet communicating with the interior of the tank is provided at a lower tip of the conical bottom and is designed as an outlet for removal of the accumulated solids. The tank is also provided with water jet nozzles that are located in the vertical wall of the tank just above the conical bottom. These water jet nozzles are used in removing solids from the tank. The water jet nozzles are angled downwardly and tangentially toward the lower tip of the conical bottom so that when water enters the tank through the water jet nozzles, the water causes a swirling action in the conical bottom that more effectively removes the solids via the solids outlet.
The conical bottom of the tank is enclosed externally with an enclosing space bounded by a flat bottom of the tank and the vertical exterior wall of the tank that surround the interior conical bottom located within the tank.
Because of the large amount of weight exerted by the water contained within the tank and the solids that accumulate within the conical bottom, the conical bottom must be well supported in order to hold all this weight. Traditional methods of providing the needed support to the conical bottom would add weight to the tank and would make it more difficult and expensive to transport and install the assembled tank at the installation site.
The present invention addresses the problems associated with constructing a conical bottom tank by providing a honey combed structure of closed pore foam within the enclosing space surrounding the conical bottom as reinforcement for the conical bottom. The closed pore foam is honey combed with several voids or compartments that fill with water as the tank is placed in service. Thus, part of the support for the conical bottom comes from the water that enters the compartments as the tank is placed into service. The foam structure provides sufficient support for the conical bottom of the tank to support it during transportation to the installation site and during installation. However, the foam structure does not provide sufficient support for the conical bottom to hold the added weight of water and solids in the tank when the tank is full.
These compartments receive water from within the tank via several downwardly facing bottom openings that extend through the wall of the conical bottom. The bottom openings are downwardly facing to prevent excessive solids from entering them as the tank is filled with water.
The bottom openings communicate between the interior of the conical bottom and a common void compartment located at the bottom of the enclosing space. Each of the compartments is in communication with the common void compartment. When the tank is placed in service, water will begin to fill the interior of the tank. As the tank fills with water, water passes through the bottom openings into the common void compartment and then into each of the compartments, filling all of the compartments with water. Air contained within each compartment is expelled into the tank as the compartment fills with water via a plurality of weep holes that communicate between the top of each compartment and the interior of the tank.
Although it would theoretically be possible to fill the entire enclosing space with closed pore foam such that the honey combing structure of the present invention would not be necessary, because of the high cost of this material, it would make the tank much more expensive.